Yusuf Zuck, transformed into the Parasitic Light, drilled into the depths of the Demon King's soul, and just as he arrived there, he saw a black halo encircling the whole soul of the Demon King.
This black halo should be the curse, laid down by the person who controls the Heavenly Demon King, Celestial King, and Human Demon King.
The reason the three kings obeyed that person was also because this black halo could control their life and death, even making them wish they were dead, or unable to live or die.
The black halo is not a substantial power, just a light, the light of the curse.
Yusuf Zuck pondered for a moment, then suddenly released a drop of the Dew of Creation.
His Dew of Creation is omnipotent; nothing in this world can resist this miraculous item, so such a minor curse should not be much of a problem.
